This invention relates to a multi-stage, reciprocating, positive displacement compressor, in which the various compression stages are coaxial one with the other.
The compressor in question is envisaged having, as the means by which it is powered, a hydraulic jack whose rod is pivotally connected to the support structure of the compressor, and whose cylinder is coaxially connected to a piston that slides in a corresponding chamber. Coaxially connected to the said piston there is a cylindrical tubular liner that is pointed towards the jack and, in a first form of embodiment for the compressor, is at least partially wrapped around the cylinder of the jack but, in a second form of embodiment, defines the circular wall of the said cylinder of the jack; the liner and the piston defining, in the said chamber, the first and the second stage of the compressor.
The two-stage compressor of the foregoing type has, compared with compressors preceding the invention (and on the basis of the compression ratio and the positive displacement capacity being identical therewith), a considerably reduced axial development and allows the cooling of the piston of the compressor to be effected in a relatively easy way.
Furthermore, because of the provision of a spherical pivot for linking the rod of the jack to the support structure of the compressor, and of an additional spherical pivot for linking the cylinder of the jack to the piston, the only necessity is that of ensuring that the two bodies, that is to say, the piston-liner assembly and the cylindrical chamber, are coaxial. This makes it possible to limit the transverse thrust of the piston on the chamber, and of the tubular liner on the guides made in one end of the said chamber and this, by causing a decrease in the specific pressure between the sliding surfaces, and thus in the heat resulting from the sliding friction, has a positive effect on the number of strokes it is possible to give the piston-liner assembly without the gaskets and the sliding rings placed on the sliding surfaces being heated or abnormally worn.
The first form of embodiment for the compressor in question also includes a type with three or four stages, the third and the fourth stage being obtained through a plunger-cylinder group, in which the rod of the plunger is coaxially connected to the aforementioned piston, on the opposite side to the jack.